1. Field of the Invention
The invention concerns a shampoo composition with improved deposition properties for anti-dandruff actives.
2. The Related Art
Many persons are victims of dandruff. The condition is manifested by little scales of dead skin formed on the scalp. White in color, the scales slough-off into the hair for an aesthetically displeasing appearance. Even more displeasing is when the little white scales are caught by the shoulder area of dark clothing. This really bothers people.
Fortunately, there are readily available remedies. Most popular are shampoos with anti-dandruff actives. Zinc pyridine thione (hereinafter “ZPT”) has been a leading active for more than half a century.
An unfortunate feature of most commercially available anti-dandruff shampoos is their harshness to the scalp. They can dry, sensitize and irritate skin. Significant culprits are the ubiquitous alkyl sulfate and alkyl ether sulfate surfactants.
Milder surfactants such as sodium cocoyl isethionate can be utilized to cleanse in a non-harsh manner. Yet, mild surfactants are not always fully successful in shampoo formulations. Problems are often encountered such as phase stability, incorrect viscosity range, and interference with deposition of actives.
Structurants have traditionally been incorporated into shampoos to adjust viscosity, maintain phase stability and deposit actives such as ZPT and silicone oils.
Commercial products have utilized cationic polymers as structurants. For instance, U.S. Pat. No. 7,541,320 (Unilever) discloses a cationically modified cellulose in a cleansing system that includes alkyl ether sulfate (3 EO), cocoamidopropylbetaine and cocoamidopropylhydroxysultaine, and as a conditioning active a non-volatile silicone.
U.S. Pat. No. 4,298,494 (Lever Brothers) reports use of a cationic derivative of polygalactomannan gum to stabilize a sodium alkyl sulfate and alkyl ether sulfate surfactant system.
Another group of commercially popular structurants are the acrylic polymers, particularly those known as Carbomers. For example, U.S. Pat. No. 5,543,074 (Chesebrough-Ponds) and U.S. Pat. No. 5,977,038 (Helene Curtis) regulate silicone deposition through use of crosslinked polymers of acrylic acid, commercially available under the trademark Carbopol®. U.S. Pat. No. 6,001,344 (Unilever) utilizes structurant combinations of xanthan gum and Carbopol® for stabilizing liquid cleansing compositions. U.S. Pat. No. 6,906,016 (Unilever) reports liquid cleansers structured with soluble and water swellable starches combined with linear C8-C13 fatty acids. U.S. Patent Application Publication 2010/0009891 (Unilever) reports personal care liquid compositions formulated with a bacterially produced microfibrous cellulose as a suspending system.
It is evident that traditional structurants used in the common alkyl sulfate and alkyl ether sulfate technology do not fully address the needs for mild liquid surfactant systems. There is a particular need to deliver anti-dandruff zinc salt actives in a cleansing medium that maintains phase stability, holds appropriate viscosity and enhances deposition of actives.